As a case study, data from several hundred samples of the thermal springs at well-known Yellowstone National Park are discussed. The pattern obtained seems to indicate: 1) geochemical similarity between the spring groups of Heart Lake, Shoshone, Upper, Midway, Lower and Norris Geyser Basins, i.e., a geochemical uniformity of major spring groups located over 40 km apart; 2) these groups may be described as originating from a common fluid, most resembling the composition of Norris waters, accompanied by CO2 and other volatiles, that react with igneous rocks, forming local variations; 3) the secondary reactions occur at (medium) depth, before the ascent to the surface; and 4) extensive concentration-dilution processes occur during the ascent to the surface.